© 2015, Springer Science+Business Media Dordrecht. R.C. Carrington, C.H.F. Peters, and W. de la Rue observed the sunspots in the second half of the nineteenth century, determining their heliographic positions between 1853 and 1870, before the solar program of the Royal Greenwich Observatory was established. The large tables of sunspot positions included in the catalogues published by these observers have recently been converted into a machine-readable format. The present work analyses these data by calculating the sunspot group velocities for each observer. The results are then fitted with a differential-rotation law to compare the data of the three observers with each other and with the results published by others. Finally, we study the possible relationship between the sunspot-group areas as determined by de la Rue and the corresponding sunspot-group velocities.
- Solar cycle, observations
- Sunspots, velocity